FIG. 1 shows an example of an electrical device 1, which in this example is an electrically powered string trimmer 1 as known in the prior art. The string trimmer 1 has a cutting end 2 which has a rotating string or strings for cutting grass, etc. At the other end, the string trimmer 1 has a handle 3 by which the operator can manipulate the device. The handle 3 has a power connection 4 by which electrical power can be supplied to the string trimmer 1.
FIG. 2 shows a detailed view of the handle 3 of the string trimmer 1. In this example, the power connection 4 takes the form of a socket 5 formed in the housing 6 of the handle 3. A power cable 7 has a corresponding plug 8 for plugging into the socket 5. The operator of the trimmer 1 connects the other end of the power cable 7 to a suitable mains electricity outlet to provide power to the trimmer 1.
Different countries have different standards and safety regulations governing the arrangement of plugs/sockets and the provision of electrical power to electrical devices. Furthermore, many countries have specific regulations governing the provisioning of power to power tools and other equipment where there is a risk of accidentally severing the electrical power cable 7. FIGS. 3 to 5 show three examples of different ways in which a power connection can be made to an electrical device 1 which are used in various countries.
In FIG. 3, a socket 5 in the form of a male connector comprising a protruding body portion 5A and conducting pins 5B which extend from the body portion 5A. The power cable 7 has a plug 8 in the form of a female connector for mating with the male connector of the socket 5. The plug 8 comprises a body portion 8A having holes 8B for receiving the pins 5B of the socket 5. The plug also has a shell portion 8C which extends beyond the body 8A and forms a receptacle in which the body portion 5A is received when the two are mated. This helps make a mechanical connection between the two parts. This also shields the pins 5B when the plug 8 and socket 5 are engaged. Such an arrangement is common for example in various European countries.
In FIG. 4, the socket 5 of the device is a male connector comprising a receptacle 5C within which the male pins 5B are positioned. The power cable 7 has a plug 8 in the form of a female connector for mating with the male connector of the socket 5. The plug 8 comprises a body portion 8A having holes 8B for receiving the pins 5B of the socket 5. The body portion 8A is received in the receptacle 5C when the two parts mate. This arrangement helps make a secure mechanical connection between the two parts as well as shielding the pins 5B. Such an arrangement is common for example in the United States of America.
In FIG. 5, the device has the cable 7 fixedly attached to the housing, i.e. there is no plug and socket arrangement to allow the cable to be connected/disconnected from the device by the operator. Such an arrangement is common for example in the United Kingdom.
It should be noted that in this document the convention is followed of referring to the connector on the electrical device as the “socket” and the connector on the power cable which moves to connect with the device as the “plug”. Also, the connector with protruding pins is known as the “male” connector and the connector with holes for receiving those pins is known as the “female” connector. Thus, the convention which is sometimes seen of always referring to the connector with the protruding pins as the plug is not necessarily followed herein. The terminology of plug/socket and male/female connector used herein is intended to be a convenient way of referring to the connector parts of the power cable/device and is not intended to be limiting unless specifically stated.
The proliferation of different arrangements for making a power connection to a device 1 creates a problem for manufacturers of such devices 1 in that to sell the device in different countries often requires redesigning the part of the device that deals with the power connection. In particular, the housing 6 of the device 1 is commonly manufactured from moulded thermoplastic or suchlike and is arranged according to the particular power connection that is required for that device 1. Thus, the manufacturer must have different tooling for manufacturing the housing of the tool for different countries. This is expensive and inconvenient for manufacturers.
According to a first aspect of the present invention, there is provided an electrical device, the device comprising: a housing; electrical circuitry in the housing, wherein the walls of the housing define a cavity having a first end that is open to the exterior of the device and a second end that is inside the housing, the housing having a first fixing arrangement at the first end of the cavity and a second fixing arrangement at the second end of the cavity, wherein the first and second fixing arrangements are each capable of fixing a power connection insert in position; and, a power connection insert fixed by either the first or second fixing arrangement, wherein the power connection insert and that fixing arrangement are constructed and arranged to mechanically interlock with each other, wherein the power connection insert provides a power cable or power connector, said power cable or power connector being electrically connected to said electrical circuitry such that external electrical power can be supplied to the device via the power cable or power connector.
By appropriate design of the insert and appropriate positioning of the insert in either the first or second fixing arrangement of the housing, the invention allows a wide range of connector types to be provided using a single design of housing. Having two fixing arrangements with different positions allows connectors to be formed using appropriate inserts that can protrude beyond the housing and that can use the cavity to provide shielding for the connection formed when a plug is plugged into that connector. Alternatively a power cable insert can be used where it is not desired to provide a connector at the device. This allows the device to be provided with an appropriate power connection type for most if not all territories in which the device may be sold. This allows manufacturers to keep down costs of manufacturing by having a single design of housing for their product, which reduces tooling costs, and which is also simple to assemble. The design can also be extended to provide different connector types if new connector types are developed in the future by designing appropriate new inserts. The invention is therefore also relatively future proof.
Preferably at least one fixing arrangement is such that there is no straight line path between the insert and the interior of the housing. This helps prevent dust, debris, etc from penetrating the housing. Potentially water can be prevented from penetrating by watertight fit between the housing and insert or by adding seals.
Preferably at least one fixing arrangement is a slot defined by the walls of the housing extending around part or all of the periphery of the cavity. Preferably the insert has a flange which fits into the slot to fix the insert in place. Preferably both fixing arrangements are defined by slots defined by the walls of the housing extending around the periphery of the cavity. These provide a secure way of fixing the insert into position which is simple to manufacture and assemble.
Preferably the first slot has a wider width that the second slot. Generally, the first slot should be wider than the cavity, so that the cavity is accessible, whereas the second slot may be smaller than the width of the cavity, which allows a smaller insert to be used to fit into the second slot.
Preferably the cavity is open or has a hole at its second end through which electrical connection is made between the insert and the electrical circuitry. Generally the electrical circuitry to which a power connection needs to be made will be accommodated within a compartment in the housing. Having an open ended cavity or a hole in the cavity allows electrical wires to be passed from the insert to the electrical circuitry.
Preferably the shape of the cavity is adapted to receive and mate with the body of a standard format connector plug. This can help retain the plug in a socket formed in the device by the appropriate insert.
In an embodiment, the insert is fixed to the second fixing arrangement, the insert having connector pins which extend into the cavity to form a connector. Thus, a socket is formed in the device by the cavity and insert to which a connector plug can be inserted to make electrical connection to the device. This arrangement can be used to provide for example a connector suitable for use in the United States of America, e.g. the connector known as NEMA 1-15 (North American 15 A/125 V ungrounded).
In an embodiment, the insert is fixed to the first fixing arrangement, the insert having a body portion that extends beyond the housing, the insert having connector pins which extend beyond the body portion to form a connector. This arrangement can be used for example to provide a connector suitable for various European countries, e.g. the connector known as the CEE 7/16 (Europlug 2.5 A/250 V ungrounded).
Preferably, the shape of the body portion of the insert is adapted to be received and mate with a shell of a standard format connector plug. This forms a connector in the device having an extending portion which can mate with part of a connector plug to keep the plug in place.
In an embodiment, the insert is fixed to the first fixing arrangement, the insert having a body with a power cable fixed thereto, the power cable extending through the body into the housing and being connected to the electrical circuitry. This can provide a means of providing power to the device without using a connector at the device suitable for use for example in the United Kingdom.
Preferably, the housing is formed in two parts which attach together to form the cavity. The housing may be formed in two halves which come together along their central plane to form the housing and to form the cavity. Thus, insert can be sandwiched between the parts of the housing as they are attached together, allowing a convenient method of manufacturing the device.